Quantum entanglement is the most difficult and confusing concept in quantum mechanics. It can be simply described as: two entangled particles in an unknown state can maintain a special correlation. Once we measure the state of one particle (for example, the spin of the particle is up, or "0"), we can instantly know the state of another particle (that is, the spin is down, or "1"), no matter how far away they are from us. Quantum entanglement is one of the most difficult concepts in physics. What is quantum entanglement? The public description of quantum entanglement must be mentioned.

Why is it a public description? Because you can't find such a description in papers or textbooks. Berchi, Bell's inequality, Bell's experiment, local realism, hidden variable theory and nonlocality will be discussed directly in the paper and teaching materials. However, in all public places, including lecturers of professional researchers, you will be told mysteriously that quantum entanglement is two particularly related particles. No matter how far apart, no matter what is blocked, as long as you move one of them (measure), the other will definitely change instantly.

Then he will tell you that he doesn't know what is going on, but the experiment proves this fact irrefutably. He can also give a seemingly simple but difficult algebraic expression to explain this entanglement relationship and prove that quantum entanglement can't transmit information.